sfc / DISM - Repair System Files

When Windows becomes unstable, or standard features such as Settings or the Start menu stop working properly, System File Checker (sfc) is one of the first things to try. It scans the protected Windows system files and replaces any that are corrupted or have been modified with the correct version.

If sfc cannot fix the problem, combine it with the DISM command, which repairs the component store that sfc uses as its source. This article explains both commands and the order in which to run them.

Preparation: run as administrator

sfc and DISM work only in a Command Prompt that is running as administrator. If you run sfc without administrator rights, it shows an error saying that you must be an administrator running a console session, and the scan does not start.

To learn how to start Command Prompt as administrator, see

Basic syntax of sfc

sfc [/scannow] [/verifyonly] [/scanfile=<file>] [/verifyfile=<file>]
    [/offbootdir=<drive> /offwindir=<Windows_folder>] [/offlogfile=<log_file>]

Scan and repair the whole system

sfc /scannow

While it runs, progress is shown as “Verification xx% complete.” Depending on your environment, it can take from several minutes to an hour or more, so do not close the window or shut down the PC in the middle of a scan.

How to read the result messages

When it finishes, one of the following messages is displayed.

Scan only, without repairing

If you only want to know the state of the system without changing it, use /verifyonly.

sfc /verifyonly

Scan and repair a specific file

If you know which file is corrupted, you can specify it by its full path.

sfc /scanfile=C:\Windows\System32\kernel32.dll

sfc /verifyfile=C:\Windows\System32\kernel32.dll

Check the details in the log

The details of sfc are recorded in C:\Windows\Logs\CBS\CBS.log. This file is very large, so it is easier to read if you extract only the sfc lines (those tagged with [SR]).

findstr /c:"[SR]" "%windir%\Logs\CBS\CBS.log" > "%userprofile%\Desktop\sfcdetails.txt"

> is redirection, which writes the output to a file. For details, see

When sfc cannot fix it: repair the source with DISM

sfc repairs files using the copies stored in the component store (C:\Windows\WinSxS). If the component store itself is corrupted, sfc cannot repair anything. In that case, use DISM (Deployment Image Servicing and Management) to repair the component store.

DISM /Online /Cleanup-Image /RestoreHealth

By default, /RestoreHealth downloads repair files from Windows Update, so an internet connection is required. It can take a long time, and the percentage may seem to stall partway through.

Order of execution

Microsoft’s guidance is to repair the source with DISM first and then run sfc. Another common approach is to try sfc first, move on to DISM only if that fails, and then run sfc once more. Either way, finish by confirming with sfc /scannow that the problem is resolved.

The steps when running DISM first are:

1. Run DISM /Online /Cleanup-Image /RestoreHealth
2. When it finishes, run sfc /scannow
3. Restart and check whether the symptoms have improved

DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannow

Run it from a batch file

Putting the steps into a batch file that runs with administrator rights saves you from typing them every time.

@echo off
net session >nul 2>&1
if errorlevel 1 (
    echo Please run this as administrator.
    pause
    exit /b 1
)

echo === Scanning and repairing the source with DISM ===
DISM /Online /Cleanup-Image /RestoreHealth

echo.
echo === Scanning and repairing system files with sfc ===
sfc /scannow

echo.
echo Done. Check the results and restart if necessary.
pause

net session fails without administrator rights, so it is often used as a simple permission check. However, in an environment where the Server service is stopped, it can fail even for an administrator. To relaunch a script automatically with administrator rights, see

DISM records detailed logs in C:\Windows\Logs\DISM\dism.log. If DISM fails, check this file as well.

Summary

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